pub fn odd_fibnacci_sum(threshold: u32) -> u32 {
    let mut sum = 0;

    let mut a = 0;
    let mut b = 1;

    while b < threshold {
        if b % 2 == 1 {
            sum += b;
        }

        let t = a + b;
        a = b;
        b = t;
    }

    sum
}
